1. Field of the Invention
This document relates to an organic light emitting diode (OLED), and more particularly, to an organic light emitting diode (OLED) including an anthracene compound.
2. Discussion of the Related Art
Recently, the importance of flat panel displays (FPD) is increasing with the development of multimedia. Therefore, various displays such as liquid crystal displays (LCD), plasma display panels (PDP), field emission displays (FED), and organic light emitting diodes (OLED) are commercialized.
In particular, an OLED has high response speed of no more than 1 ms, uses a small amount of power, and is self-emissive. In addition, since there is no problem in a viewing angle, the OLED is advantageous as a moving picture display medium regardless of the size of an apparatus. In addition, since the OLED may be manufactured at a low temperature and has simple manufacturing processes based on a conventional semiconductor process technology, the OLED is spotlighted as a next generation FPD.
The OLED includes a light emitting layer between an anode electrode and a cathode electrode so that holes supplied from the anode electrode and electrons supplied from the cathode electrode are combined with each other in the light emitting layer to form excitons that are pairs of holes and electrons. Light is emitted by energy generated by the excitons returning to a ground state.
The OLED is developed to have various structures. Among them, a tandem-type OLED in which a number of light emitting layers are laminated is developed. The tandem-type OLED has a structure in which a plurality of stacks each formed of a hole injection layer (HIL)/a hole transport layer (HTL)/a light emitting layer/an electron transport layer (ETL)/an electron injection layer (EIL) are laminated between the anode electrode and the cathode electrode. In particular, a charge generation layer (CGL) formed of an N-type CGL and a P-type CGL is provided between the stacks to generate charges or to inject charges into the light emitting layers.
However, in the CGL, due to a difference in an energy level between the N-type CGL and the P-type CGL, a characteristic in which electrons generated in an interface between the P-type CGL and an adjacent hole injection layer by charge generation are injected into the N-type CGL is deteriorated. In addition, when the conventional N-type CGL is doped with an alkali metal, the alkali metal is diffused into the P-type CGL so that the life of the OLED is reduced.